<p><it>Abstract—</it>This paper proposes a simple, yet effective scheme to prevent congestion in a packet-switched multistage interconnection network (MIN) caused by <it>hot spots</it>. In this scheme, switches in the second and third stages of the MIN monitor their buffer occupancy to detect any notable nonuniform access behavior. When a switch detects congestion, packets generated by processors will be blocked from entering the congested switch until the congestion is cleared. Our scheme is compared with two well known schemes [<ref type="bib" rid="D05351">1</ref>], [<ref type="bib" rid="D05352">2</ref>], and shown to exhibit significantly better performance than these two.</p><p><it>Index Terms—</it>Congestion tree, packet-switching, multistage interconnection networks (MIN), hot spots, buffer occupancy.</p>